Kiln system and method of operation



p 1947- E. T. MANKIN KILN SYSTEM ANDv METHOD OF OPERATION.

2 SheetESheet 1' Filed Aug. 2, 1945 JNVENTOR: .Ejiwarfl 21' Mankc'n,

Sept. 30, 1947.

E. T. MANKIN KILN SYSTEM AND METHOD OF OPERATION Filed Aug. 2,1945 2 Sheets-Sheet 2 iNVENTOR:

Edward TManZct'n,

Patented Sept. 3Q, 1947 UNITED STATES PATENT OFFICE KILN SYSTEM AND METHOD OF OPERATION Edward T. Mankin, Richmond, Va.

Application August 2, 1943, Serial No. 497,073

14 Claims.

The present invention relates to the operation of firing instrumentalities and more particularly to an arrangement of burning kilns and method of operation thereof.

Yet more specifically the present invention contemplates the improved utilization of heat liberating standard firing kilns for the purpose of water-smoking and/or preheating additional kilns, thus resulting in an effective utilization of energy which might otherwise be dissipated as waste heat.

While I am aware that attention over a number of years has been directed to this general problem, nevertheless the proposals previously advanced for overcoming this difiiculty have involved many inherent objections. Thus, for example, it is possible to effect a more rapid and eificient utilization of the heat energy expended where the firing instrumentalities are materially modified in structure. In many instances of a which I am aware the resulting construction has involved the provision of complex and costly instrumentalities bearing no substantial similarity to the conventional kiln and necessitating complete replacement thereof. Even the less modified kiln constructions hitherto proposed, embody a distinct revision of the structure through the provision of additional internal flues and ducts with accompanying complexity of flue and draft structure. The operation of such kilns is thus rendered correspondingly difficult and complex and the limited advantages thereof are unavailable in the absence of a material investment for replacement construction.

The present invention on the other hand contemplates the operation of standard kilns of the well known type and particularly the conventional individual, downdraft ceramic firing kilns, in such a manner as to achieve all the advantages of continuous operation by only a minor modification of the flue arrangement. Yet more particularly, the present invention contemplates utilization of the single outlet flue of each kiln for conveying heat in both directions under the influence of a suitable control instrumentality whereby to re-utilize substantially all of the heat which hitherto has been wasted at the stacks.

It is accordingly an object of the present invention to provide a new and improved method of operation of standard downdraft kilns capable of utilizing the burning heat in watersmoking and preheating.

Another object of the invention contemplates a system and process as above wherein the charge is subjected to watersmoking and preheating by heated gases passing upwardly and later outwardly, under increasing pressure, in order to effect a uniform heating from an internal heat source within the kiln adjacent the floor.

Yet more specifically it is a further object of the present invention to provide a kiln operating method as above, wherein the charge subjected to treatment, as for example, a mass of unfired brick, i initially subjected to heating by an updraft of heated gases, which as preheating progresses are A directed gradually outwardly through the entire mass of ware, and particularly wherein after reaching adequate preheating temperature the flow of gases may be reversed and the kiln operated downdraft in the conventional manner to complete the final firing and to afford a supply of heated gases for initiating the operation of subsequent kiln units,

The invention is illustrated more specifically in the accompanying drawings, wherein Figure 1 represents more or less diagrammatically a plan arrangement with a series of kilns connected for operation in accordance with the principles herein set out;

Fig. 2 is a view in central vertical cross-section of a kiln with the crown vents open, the circulation of heated gases in this showing being substantially as indicated by the small arrows;

Fig. 3 is a view similar to Fig. 2 but with the central crown vent closed;

Fig. 4 is a viewsimilar to Figs. 2 and 3 with the small arrows indicating the flow of gases with all crown vents and bafiies closed; and

Fig. 5 is an end view partly in elevation and partly in vertical cross-section of induction or fan arrangement.

Referring to the drawing wherein one preferred illustrative arrangement is disclosed merely for purposes of general exemplification, the numeral It] indicates a plurality of brick firing kilns. It is important to note that each of these kilns in the present instance represents a kiln of the standard downdraft type, at present having wide conventional use. While it will be apparent that the present invention may be applicable to closely equivalent types of kiln, the foregoing constitutes a preferred embodiment for the present purpose.

As shown, kilns of the present type comprise an annular wall I2 surmounted by a dome or crown l4 having a plurality of vents. The outer vents-l6, as well as the centrally located vent l8, are provided with the usual damper or throttle control adapted to permit restriction or dampering of the internal gases. Internally each kiln is provided with a perforated floor or platform 20 for supporting the charge. While in conventional constructions the floor 20 may assume various forms, the characteristic construction shown involves a checkered structure formed of suitable refractory material and providing a multiplicity of openings 22 for conducting a flow of gases therethrough. The floor is supported by a suitable supporting structure affording a plurality of main and auxiliary fines communicating with the apertures 22. In normal operation, therefore, the brick is so stacked upon the floor as to afford communication at all times between the internal spaces in the charge and the lower flues of the kiln.

The floor of the kiln supports an annularly disposed series of bag walls 24 defining the pockets or firing recesses for the fuel employed in the final operation of the device. Each firing recess is provided with an opening to outside atmosphere, capable of being closed, throttled or dampered by a door or adjustable baflie 25. Below the lower fiues the kiln is, as shown, provided with a bottom base or supporting structure 26.

In accordance with the usual arrangement of the present downdraft kilns the main internal fines of each kiln communicate with a single outlet flue 28 which extends usually at a low level beneath the ground, to a dampered smoke stack 3!! or other suitable point of release. The heat energy therefore passing from the kiln is thus largely wasted.

When operating in accordance with the present invention the flue 28 and the stack may be, as shown in the drawings, permitted to remain for operation under abnormal conditions but they may be equally as well omitted or discarded.

The main flue of each of the kilns, however, is connected directly with an auxiliary heat flue 32 which is suitably carried to a central draft induction means 33. Thus it will be seen that the righthandmost kilns of Fig. l communicate through fines 3! with a single fiue 32 leading to the fan. The remaining kilns are similarly arranged in paired arrangement although it will be appreciated from an understanding of the following description that the specific arrangement of the fiues may be substantially modified in accordance with the principles of the present invention.

The induction or fan system, as shown more clearly in Fig. embodies any suitable draftpressure or flow-creating instrumentality; in the present instance comprising preferably a pullpush type of induction fan driven by an electric motor 38 and suitably water-cooled. In general the several heat flues come together in a central manifold or gathering portion 38 from which the fan derives its supply of gases. To this end each of the conduits or flues 32 is provided with a suitable damper 40 and the inlet duct 42 of the fan extends into the intermediate space in the manifold. The fan body is identified by reference numeral M and the outlet or exhaust conduit or duct 46 thereof is arranged to communicate selectively with any of the heat flues 32. To this end the fan in the embodiment shown is rotatably mounted over the manifold so that the laterally extending outlet duct 46 may be swung to position about any one of the fines. When so arranged the outlet 46 is constructed to fit and seat snugly upon the margins of a flue aperture for supplying, preferably under appreciable pressure, the discharge of the fan. The flue openings or apertures 48 when not connected with the fan may be maintained closed by suitable coverings, dampers or doors 53. Additional dampers 52 are provided in heat fiues 3! for use as required. Dampers 54 associated with the stack are normally maintained closed as indicated above.

With this arrangement it is quite apparent that the heat from any of the kiln flues 3! may be selectively withdrawn and redirected into another kiln. Alternatively the fiow may be reversed when the last-named kiln is under fire, the gaseous products thereof being selectively introduced into the first-named kiln to preheat a charge where desired. It is, of course, necessary to close the damper 40 in the flue 32 to which the fan supplies the gas under pressure as well as all of the other fiues 32 with the exception of the one furnishing waste heat.

The invention particularly contemplates the operation of the foregoing system of kilns in accordance with a preferred sequence of steps as follows: If it be assumed that one Or more of the righthandmost kilns are in operation with the fuel burning in the bag walls then the fan 33 may be disposed to communicate at its outlet with one or more of the kilns shown in the central upper portion of Fig. 1 while drawing heat from the fiue 32 communicating with one or more of the first-named kilns. Accordingly, therefore, the damper 40 associated with the heat supplying flue 32 is open whereas the remaining dampers 40 are closed.

The first-named kiln or kilns at this point contain a charge of ware under fire, as above, whereas the second kiln or group of kilns has just been charged with unfired ware from the driers. Accordingly, therefore, the fan draws the exhaust heat from the floor of the kiln under fire and directs it underground into the main flues of the kiln containing the fresh ware.

It is important to note that during this initial phase of operation the kilns being heated by the waste products from the kiln under fire, pass through a watersmoking period during which time the last residual traces of moisture are removed from the ware and an initial elevation in temperature is effected. The incoming hot gases pass upwardly through the floor of the kiln and through the ware in such a manner as to permit slow even transfer of heat. .To this end the crown vents I6 and [8 are opened at least partially or fully, permitting the main flow of the gases to pass outwardly after having contacted the contents of the kiln. During this time it should be noted that the doors or bafiles 25 leading to the bag wall or fuel compartments 24 are at least partially throttled so that only a portion of the gases moves laterally within the kiln. This phase of the operation results in a final temperature of 550 to 700 C. and requires a period of 12 to 16 hours.

During the succeeding or second phase of the operation the central vent I8 is closed and the outer crown vents 16 preferably throttled materially. The doors or baffles 25 remain partially open so that the path of the incoming gas is thus gradually deflected. At this time an increasing proportion of the hot gases moves. laterally through the mass of ware. As a result of the somewhat increased restriction of the outlets, the pressure in the kiln is increased a small amount and the preheating is accordingly found to progress more rapidly and efficiently. This operation is continued until the ware has reached the temperature of about 1000 F. At this time the vents I6 and I8 are completely closed so that the doors or baffles to the bag wall compartments form the sole outlet. These are restricted somewhat further so that an increased pressure is maintained within the kiln. As a result the incoming gases after rising upwardly are entirely deflected laterally and outwardly through the bag wall openings. Operation is thus continued until the ware has reached the maximum practical temperature attainable by the waste gases available.

By this time, however, the fuel previously placed within the bag walls will have become ignited by the heat from the ware and the preheated kiln is thus placed in condition for the final stage of operation at which it commences supplying its own heat from the burning fuel, to the adjoining furnace walls. When this point is reached the dampers are readjusted and the fan again rotated to supply the products of combustion of this kiln to any of the additional kilns which in the meantime have received a fresh charge of ware. The fires are attended and the kiln operates under fire in its normal downdraft manner to complete the operation. Operatlon may proceed indefinitely as above so that the waste heat from any kiln under fire is supplied to Watersmoke and preheat the next succeeding kiln or kilns ready for operation.

It is important to note, however, that when the final firing of any kiln commences the flow of gas in the kiln fiue is reversed and the same heat flue 3! which was previously employed to supply heated gases is utilized to withdraw heat in the reverse direction; the flow of gases progrossing through the doors to the bag wall recesses, inwardly through the ware and thence down- Wardly through the checkered floor of the kiln. It is furthermore important to note that the present method of operation results in not only a material saving in fuel but improved efficiency in general operation and in the character of the product produced. Thus it has been found that operating in accordance with the foregoing series of heating phases the were is more regularly uniformly heated and results in a higher yield of product than where the kilns are operated in the conventional manner. The ctual time of burning may be decreased by as much as 45 per cent without detriment to the product. While no theoretical explanation is available for this effect, it may be accounted for in part at least by maintenance of an initial upward flow of gases during the phase of watersmoking, followed by the gradual changing of the main fiow to a lateral direction so that the ware is heated first internally and then outwardly from the center. It is thought, moreover, that the gradual increase in pressure as the flow is diverted serves to appropriately adjust the rate of heat transfer to the ware and maintain it at an optimum. Final reversal of the fiow with firing at the bag walls seems to have a valuable effect and assures an efficient, rapid and regular disposition of the heat throughout the mass of ware in such a manner that the entire content reaches the final firing temperature rapidly and uniformly.

In fact, when preceded by the initial heating stages specified, the final firing or soaking period may be completed in many instances in 72 hours although additional heating times may be employed in firing especial refractory material or in instances where the firing process tends to advance ahead of the rate at which ware may set.

It will be apparent from the foregoing that the present invention provides a direct, continuous burning available by slight modification of the standard downdraft kiln fiue arrangement. Only minor additional equipment is necessary. It will be evident, moreover, from the foregoing that construction lends itself readily to the use of automatic controls for redirecting the gases selectively to each of the kilns as the charge of ware being heated reaches a predetermined temperature. It is furthermore significant to note that the present process interferes in no way with the utilization of waste heat for drying purposes. Thus, after completion of the burning period the contents of any kiln are at sufficient temperature to provide all of the heated gas necessary to operate the drying plant without interfering with the progress of the present process.

It will be appreciated from the foregiong that the structure disclosed may be variously modified in accordance with the principles of the present invention and the arrangement of the fan and flues may take a multitude of various forms. Thus, in place of the paired arrangement of kilns, each kiln may be individually connected with the central fan, or separate groups of any desired number may be so associated. Probably the most important consideration to be observed is the arrangement of the single kiln flue of each kiln so that it may be used either as an inlet or outlet duct for selectively carrying the combustion products of any burning kiln to any other kiln in the system.

The fan or induction means may take various forms and the outlet construction thereof may, if desired, comprise a series of fixed communicating ducts suitably valved for directing flow; or a flexibly mounted conduit adapted to be selectively engaged with the required duct or ducts may be provided. In such cases it is not necessary to provide a rotatable mounting for the fan. The flues may be so connected that any required number of kilns may be preheated at the same time.

While the foregoing describes the preferred forms of the invention for purposes of illustration, it is to be understood that the invention is not so limited but may have various forms in accordance with the claims, hereinafter appended.

What I claim is:

1. The method of operating a plurality of standard downdraft brick kilns having peripherally disposed firing means, a vented crown and an apertured ware supporting floor with an outlet heat flue therebeneath, which comprises withdrawing products of combustion from the outlet heat flue of a brick kiln under fire and forcing said products through the outlet flue of a second kiln and through a mass of freshly set unfired ware in the second kiln, continuing the heating of the unfired ware while discharging a substantial portion of the heating gases through the central portion of the second kiln crown, restricting said discharging means when the watersmoking period is completed and exhausting the major portion of the heating gases at the lateral peripheral margins of the second kiln thereafter until the ware has been uniformly preheated prior to direct firing.

2. The method of operating a plurality of standard downdraft brick kilns having peripherally disposed firing means, a vented crown and an apertured ware supporting floor with an outlet heat flue therebeneath, which comprises withdrawing products of combustion from the outlet heat flue of a brick kiln under fire and forcing said products through the outlet flue of a second brick kiln upwardly through a mass of freshly set, unfired ware in the second kiln, continuing the heating of the unfired ware while discharging heating gases through central vents of the second kiln crown, closing said discharge means at the central portion of the crown when the watersmoking period is completed and thereafter for a substantial period discharging the gases through the firing means of the second kiln and through marginally disposed vents of the second kiln crown until the product has been preheated.

3. The method of operating a plurality of standard downdraft brick kilns having peripherally disposed firing means, a vented crown and an apertured ware supporting floor with an outlet. heat flue therebeneath, which comprises withdrawing products of combustion from the outlet heat flues of a brick kiln under fire and forcing said products through the outlet fine of a second brick kiln upwardly through a mass of freshly set, unfired ware in the second kiln, continuing the heating of the unfired ware while discharging heating gases through central vents of the second kiln crown, restricting said central vents when the watersmoking period is completed, thereafter for a substantial period discharging the gases through the firing means of the second kiln and through marginally disposed vents of the second kiln crown, and subsequently restricting all of said crown vents and heating the ware while the gases are exhausted through the peripherally disposed firing means.

4. The method of operating a plurality of standard downdraft brick kilns having peripherally disposed firing means, a vented crown and an apertured ware supporting floor with an outlet heat fiue therebeneath, which comprises withdrawing products of combustion from the outlet heat flue of a brick kiln under fire and forcing said products through the outlet flue of a second brick kiln upwardly through a mass of freshly set unfired ware in the second kiln, continuing the heating of the unfired ware while discharging heating gases through central vents of the second kiln crown, restricting said central vents when the watersmoking period is completed, thereafter exhausting the heating gases adjacent the lateral peripheral portions of the second kiln until the ware has been uniformly preheated prior to direct firing, discontinuing the incoming flow of gas when the second kiln has been preheated, and placing the second kiln under fire and reversing the direction of gas flow in the second kiln flue to draw products of combustion from the firing means inwardly through the ware and. downwardly through the supporting floor.

5. The method of operating a plurality of standard downdraft brick kilns having peripherally disposed firing means, a vented crown and an apertured ware supporting floor with an outlet heat flue therebeneath which comprises withdrawing products of combustion from the outlet heat fiue of a brick kiln under fire and forcing said products through the outlet flue of a second brick kiln upwardly through a mass of freshly set unfired ware in the second kiln, continuing the heating of the unfired ware while discharging heating gases through central vents of the second kiln crown, restricting said central vents when the watersmoking period is completed, thereafter for a substantial period dis charging the gases through the firing means of the second kiln and through marginally disposed vents of the second kiln until the product has been preheated, discontinuing the incoming flow of gas when the kiln has been preheated, and placing the second kiln under fire and reversing the direction of gas flow in the second kiln fiues to draw products of combustion from the firing means inwardly through the ware and downwardly through the supporting floor.

6. The method of operating a plurality of standard downdraft brick kilns having peripherally disposed firing means, a vented crown and an apertured ware supporting floor with an outlet heat flue therebeneath'which comprises withdrawing products of combustion from the outlet heat flue of a brick kiln under fire and forcing said products through the outlet flue of a similar brick kiln upwardly through amass of freshly set, unfired ware in the second kiln, continuing the heating of the unfired ware while discharging heating gases through central vents of the second kiln crown, restricting said central vents when the watersmoking period is completed and thereafter for a substantial period discharging the gases through the firing means of the second kiln and through marginally disposed vents of the second kiln crown at a somewhat increased pressure, subsequently restricting all of said crown vents and heating the ware while the gases are exhausted under a further increased pressure through the peripherally disposed firing means, discontinuing the incoming fiow of gas when the second kiln has been preheated, and placing the second kiln under fire and reversing the direction of gas flow in the second kiln flue to draw products of combustion from the firing means inwardly through the ware and downwardly through the supporting floor.

7. In a firing system for the burning of refractory ware and the like, a plurality of separate downdraft kilns, each provided with peripherally disposed firing means and having a supporting floor for the ware provided with apertures distributed over its area, and an outlet heat flue in connection with said apertures; a manifold into which all of the fines are directed, and means associated with the manifold for withdrawing the products of combustion from the outlet fiue of one or more of said kilns and directing said products under pressure to the heat flue of one or more of the remaining kilns for delivery through the floor apertures thereof.

8. In a firing system for the burning of refractory ware and the like, a plurality of separate downdraft kilns, each provided with peripherally disposed firing means and having a supporting floor for the ware provided with apertures distributed over its area, and an outlet heat flue in connection with said apertures; a manifold into which all of said flues are connected, and a gas propelling and selective delivery means associated with said manifold and arranged to withdraw combustion gases from the heat flue of one or more of said kilns and direct said gases selectively under pressure into the heat flue of one or more of the remaining kilns for delivery through the floor apertures thereof.

9. The method of operating a plurality of downdraft kilns each having peripherally disposed firing means, adjustable vents, a supporting floor for the ware provided with apertures distributed over its area, and an outlet heat flue in connection with said apertures; which comprises withdrawing products of combustion from the outlet flue of one of the kilns, forcing said products through the outlet flue of another kiln and through the floor apertures thereof, and

9 controlling the escape of said products from said other kiln through the vents thereocf whereby to control the pressure therein.

10. In a firing system for the burning of refractory ware and the like, a plurality of separate downdraft kilns, each provided with peripherally disposed firing means and having a supporting floor for the ware provided with apertures distributed over its area, and an outlet flue in connection with said apertures; a manifold in connection with all of said fiues, dampers for controlling said fiues, respectively, and gas impelling means in connection with the manifold arranged to withdraw the products of combustion from the heat flue of one or more of said kilns and deliver said products under pressure to the heat flue of one or more of the remaining kilns and through the floor apertures thereof when said dampers are appropriately adjusted.

11. In a firing system for the burning of refractory ware and the like, a plurality of separate downdraft kilns each provided with peripherally disposed firing means and having a supporting fioor for the ware provided with apertures distributed over its area, and an outlet heat flue in connection with said apertures; a fan having an intake side and an output side, and means for reversibl associating said sides with a pair of outlet flues so as to be able to withdraw combustion gases from either of the associated outlet flues and to push the withdrawn gases into the other associated flue.

12. In a firing system for the burning of refractory ware and the like, a plurality of separate downdraft kilns each provided with peripherally disposed firing means and having a supporting floor for the ware provided with apertures distributed over its area, and an outlet heat flue in connection with said apertures; a flue connecting the outlet flues of the kilns, a fan, a connection between the fan intake and said connecting flue, dampers in said connecting flue at the sides of said connection respectively, and means whereby the fan output is connectible into said connecting flue outwardly of any one of said dampers, whereby by appropriately adjusting said dampers combustion gases can be pulled from any one 6f the kilns and pushed into another through the floor apertures thereof.

13. In a firing system for the burning of refractory ware and the like, a plurality of separate downdraft kilns, each provided with peripherally disposed firing means and having a supporting floor for the ware provided with apertures distributed over its area, and an outlet heat flue in connection with said apertures; a manifold into which all of the fiues are directed, means associated with the manifold for withdrawing the products of combustion from the outlet flue of one or more of said kilns and directing said products under pressure to the heat flue of one or more of the remaining kilns for delivery through the floor apertures thereof, and adjustable vent means in the kiln crowns for the control of the pressure in said remaining kiln or kilns,

14. In a firing system for the burning of refractory ware and the like, a plurality of separate downdraft kilns, each provided with peripherally disposed firing means and having a supporting floor for the ware provided with apertures distributed over its area, and an outlet heat flue in connection with said apertures; a manifold into which all of said fiues are connected, a gas propelling and selective delivery means associated with said manifold and arranged to withdraw combustion gases from the heat flue of one or more of said kilns and direct said gases selectively under pressure into the heat flue of one or more of the remaining kilns for delivery through the floor apertures thereof, and adjustable vent means in the kiln crowns for the control of the pressure in said remaining kiln or kilns.

EDWARD T. MANKIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain 1927 Number Number 

